Opto-matrix frames have been developed which utilize rows of light sources called phototransmitters and rows of light detectors called photoreceptors arranged in X and Y arrays to effectively cover a given area. The light beams propagated over such area may be selectively broken by the insertion of a stylus such as a finger to provide an electronic signal. This signal is in fact the absence of light, in reality, a shadow created by the stylus detected by appropriate receptors. Such frames have found widespread use in touch input or touch screen entry devices wherein the frames are fitted over the information display units of computers and the like. U.S. Pat. No. 4,267,443 titled "Photoelectric Input Apparatus" issued May 12, 1981 to Carroll et al. relates to the use of an opto-frame.
Large opto-frames have also been conceived for providing security or safety in order to alarm and/or arrest the movement of machinery or to prevent entry in unauthorized areas by either personnel or, for example, the hand of an operator of a punch press relative to the closure of dies in the press.
As a general rule, the cost and complexity of opto-frames has heretofore been proportionate to the number of transmitters and receptors. This number is proportionate to either the size of the area to be covered or to the resolution of the size of the stylus employed. As a general rule, the closer together physically the light elements, both receptors and transmitters, the higher the resolution or the ability to distinguish coordinate locations of a stylus or finger penetrating the light beam array. Also as a generalization, the largest part of the cost of opto-frames is for the receptors and transmitters and associated circuitry.
With this understanding as background, it is an object of the present invention to reduce the cost of opto-frames by reducing the number of light elements and associated drive circuits from that heretofore utilized. It is a further object of the invention to reduce the complexity and cost of the opto-frames and other area scanning optical systems for detection and coordinate location purposes by substituting reflecting means for numbers of transmitters or, alternatively, substituting reflecting means for detectors.
It is still a further object of the invention to employ holographic techniques to generate reflecting surfaces capable of directing light received from a single source over a broad area; or, alternatively, reflecting light from multiple sources to a single light receptor location in order to reduce the number of light elements employed in opto-frames. It is a final object of the invention to provide a novel technique of reflecting light for a variety of useful purposes.